In modern power generation plants and other manufacturing industries that require large volumes of water, there is a widely recognized problem that there is a potential loss of water caused by the adherence to and buildup of a variety of foreign substances on the exposed surfaces of fluid transport systems. The exposed surfaces, of the fluid transport systems, include, but are not necessarily limited thereto, the inner surfaces of the water intake pipes, valves, fittings, heat exchangers, etc, and the outer surfaces of screens (rotary & bar), etc.. Power generating plants and other manufacturing facilities which require the use of a particular fluid medium, such as fresh water, have long sought an effective method of maintaining these fluid transport systems operational and free of any buildup of foreign organisms and/or other debris.
One such foreign organism of particular concern, which were discovered recently in North American lakes and streams, is the Zebra Mollusks. Such Zebra Mollusks are better known in the art as Zebra Mussels. See, for example, an article published in the December 1990 issue of "Electrical World" pages 72-74 and an article published in the July 1990 issue of "The Atlantic Monthly" on pages 81-87. The disclosures of these particular articles are incorporated herein by reference thereto.
Prior to the present invention, when the fluid transport systems, of current technology, exhibit diminished capacity due to clogging by foreign substance buildup, one method of servicing a submerged piping system would be to have a person manually pull a dragging device through the fluid transport system to dislodge the buildups and/or clogs and subsequently pull them through to the exit end of the piping system for manual cleanup. Serious drawbacks to this prior art method are readily apparent and would at least include the fact that this method is not only labor-intensive but also time-consuming. In addition, this method cannot be accomplished continuously, but must be done on a regularly scheduled basis.
Another cleaning method in use, prior to the present invention, for facilities, such as water treatment plants, includes flushing the fluid transport system with relatively large quantities of chemicals. These chemicals include chlorine or potassium chloride. While this prior art process can be conducted in a more or less continuous manner, it is not efficient or cost-effective to induce large quantities of chemicals into the desired fluid medium. Furthermore, in some cases, these chemicals may be detrimental and must later be separated out. Separation of these chemicals from the fluid medium will obviously add to the operating cost of the facility. This cost is then passed on to the consumers.
As discussed in the above-referenced articles, at least three types of problems have already been identified with Zebra-Mussel fouling in water intake systems. Initially, layers of attached mussels will reduce and eventually block the flow of the fluid medium through such intake systems. This reduced and/or blocked flow will occur even through relatively large-diameter piping, trash racks, and traveling screens. Eventually, shells or clumps of shells breaking free of their attachment sites can block the openings in down stream piping, heat exchangers, strainers, or traveling screens. Finally, the Zebra Mussel attachment points will accumulate other debris and serve as sites for detrimental corrosion. There are a number of Environmental Protection Agency (EPA) approved chemical methods that have been tried in US powerplants. These methods include chlorination, the most discussed method; bromination, primarily Acti-brom, a Nalco Chemical Co (Naperville, Ill) product; and Betz Laboratories' (Trevose, Pa.) Clam-trol. Several other chemical treatments have been tried in laboratory tests, but not in a utility or industrial environment. Chlorination is the most common chemical control for Zebra-Mussel fouling. Continuous chlorination at 0.3 ppm for up to three weeks is required to achieve efficacy. Intermittent chlorination programs, that feed a few hours daily have generally been found to be ineffective. Using other chemicals-such as ozone, hydrogen peroxide, and potassium permangenate is possible, but expensive, environmentally unsound, and/or impractical to distribute throughout a cooling system.
It has been reported that Detroit Edison is trying to control Zebra Mussels by scraping and hydroblasting during regularly scheduled maintenance. Janiece Romstadt, on the other hand, has received federal permission to use a commercial mollucicide. Ontario Hydro is treating some of its coolant with hypochlorite, an oxidant that chews away at the soft parts of the organism and is the active ingredient in household bleach; the utility admits, however, that this short-term solution is offensive to the general public anxious about the environment. One other alternative is ozonation. Like hypochlorite, ozone is an oxidant; it is also environmentally benign. But it is extremely expensive. Ontario Hydro estimates that ozonation would cost them about $9 million per plant.
One member of the U.S. Fish and Wildlife Service, puts the bill for re-engineering, maintenance, and other forms of Zebra Mussel abatement at almost half a billion dollars a year. But none of the emergency measures tried to date, even though they may alleviate specific problems here and there, will do anything to halt the overall proliferation of Zebra Mussels. These mussels are very strongly byssate and they will attach to the insides and occlude the openings of industrial and domestic pipelines, clog underground irrigation systems of farms, greenhouses, and any other facility that draws water directly from a body of water containing these mussels, encrust navigation buoys to the point of submerging them, and encrust hulls of boats and other types of sailing craft that remain in the water over the summer and fall. The mussels may also become a significant vector of parasites that are lethal to game species of waterfowl and fish.
In the November 1991 issue of "Underwater USA" a news article appeared which indicated that, the tiny but dreaded Zebra Mussel has been discovered for the first time in a section of the Mississippi River near La Crosse, Wis., a U.S. Fish and Wildlife Service toxicologist reports.
Another expert says that he expects to see the Zebra Mussel population explode by next year. Worse, it's likely that boaters will inadvertently introduce the Zebra Mussels to Minnesota lakes. These mussels have an extremely hard shell and clog water intakes at power plants and municipal water systems. For example, the Monroe, Mich., water supply system was crippled for three days when the mussels clogged an intake pipe. Consequently, the consumers water bills increased 18 percent to pay for the cost of removing them.
An Ontario electric company spent $10 million on chlorine to keep the mussels out of power plant water intake pipes.
This same expert expects the same things to happen at power and water plants located along the Mississippi River. He says locks and dams also are favored attachment sites for the mussels, which cause leaks and prevent flood control gates from closing completely.
It can be seen from the above discussion that control of living marine organisms in a body of water, such as lakes and rivers, is a significant problem. It is also evident that not one of the solutions, suggested in the prior art to date, have been totally effective in controlling the problem.
It can also be seen from the above description that, to the best of applicants knowledge, no attempt has been made to control adherence to and buildup of Zebra Mussels on exposed surfaces of submerged components and structures using an electrical field.